Method of making cross-lapped spread webs

ABSTRACT

MAKING NON-WOVEN FABRICS WHICH LOOK LIKE WOVEN CLOTH BY STRIATING A WEB OF CRIMPED PARALLEL FILAMENTS, SETTING THE STRIATED WEB, AND CROSS-LAPPING THE STRIATED WEB.

Nov. 30, 1971 G. A. WATSON METHOD OF MAKING CROSS-LAPPED SPREAD WEBSOriginal Filed Jan. 5, 1967 /3 l r d INVENTOR.

GEORGE A. WATSON ATTORNEY United States Patent 3,623,927 METHOD OFMAKING CROSS-LAPPED SPREAD WEBS George A. Watson, Charlotte, N.C.,assignor to Celanese Corporation, New York, N.Y.

Original application Jan. 3, 1967, Ser. No. 606,984, now Patent No.3,515,621, dated June 2, 1970. Divided and this application July 25,1969, Ser. No. 871,079

Int. Cl. 1832b 5/02, 31/04 US. Cl. 156-161 5 Claims ABSTRACT OF THEDISCLOSURE Making non-woven fabrics which look like woven cloth bystriating a web of crimped parallel filaments, setting the striated web,and cross-lapping the striated web.

This application is a divisional application of Ser. No. 606,984, filedJan. 3, 1967, now Pat. No. 3,515,621.

This invention relates to novel non-woven products made from spread websof continuous filaments, and to processes for the manufacture of suchproducts.

In accordance with one aspect of this invention, I have produced new anduseful non-woven products, having much of the appearance and strength ofa woven fabric, from tows of continuous filaments. This can beaccomplished by spreading the tow to form a thin web having spacedlongitudinal striations, of alternating dense and lean areas, across itswidth, setting said striations in said web, cross-lapping the setstriated web, and bonding adjacent layers of the cross-lapped structure.The whole structure can be produced in one continuous operation, withoutthe need of the discontinuous steps employed in the manufacture of wovenfabrics.

The production of a thin, diaphanous spread web may be effected in themanner described in the US. Pat. No. 3,156,016, by subjecting a crimpedtow band, having crimps in widthwise registry, to a cr-imp-deregisteringoperation followed by a spreading operation. The tow band may contain,for example, about 5000 to 1,000,000 parallel continuous filaments, andthe crimps may be produced by passing the tow through a stuifer-boxcrimper, of conventional type, giving a tow band having ridges andtroughs, formed by aligned crimps in adjacent filaments, extendingtransversely of the band. In a typical deregistered, spread lightweightweb, all the continuous filaments run in the same general direction,lengthwise of the web. However, when one does not look at the whole of along length of any particular filament, but looks instead at theindividual crimps thereof, it will be seen that most portions of thefilament do not run in this general lengthwise direction but, instead,zigzag back and forth across such general direction. The amplitude ofthe crimps is such that, for any particular filament, the portion of thecrimp at one side (hereafter termed the crest of the crimp) overlaps oneor more neighboring filaments while the portion of the crimp at theother side (hereafter termed the valley of the crimp) overlaps one ormore of its neighboring filaments on said other side. This overlap helpsto give the webs their cohesiveness. For example, the filaments in theweb may have a crimp whose amplitude (from a median line running in thesame direction as the filament) is in the range of about to A inch, saidamplitude being measured from said median line to the top of a crest, orto the bottom of a valley. Since there may, for example, be severalhundred filaments per inch of web width and since the crimps are not inregistry, there will be considerable overlapping of filaments in theweb.

When one turns from an examination of the crimps and takes a somewhatlarger, though still relatively short,

3,623,927 Patented Nov. 30, 1971 view of the portion of any particularfilament which contains several crimps, and which may be, for example,/2 inch to several inches long, it will be found that these portions arenot prefectly parallel to the longitudinal direction of the web, butmake small angles therewith, which angles change in direction andmagnitude along the length of the filament; generally these angles areless than 20, although for very short portions (e.g. /2 inch long) theangle may be larger at times.

It is believed that the overlapping of the crimps and the overlapping,due to the presence of the angularly disposed short portions, justdescribed, contribute to the cohesiveness of the web so that, despiteits fineness, it can be readily handled as a unitary structure. Thedegree to which the individual filaments meander by virtue of thepresence of said crimps and angularly disposed short portions is not,however, very great; typically, the ratio of the straightened lengths ofthe individual filaments to the lengths of the same filaments in the webis less than about 11/2:l and, preferably, greater than 1.1: 1, e.g.about 1.2:1 to 1.4:1. This ratio may be measured by cutting apredetermined length of the web, removing the individual filaments ofthe cut portion and measuring their lengths while under a tension justsufficient to remove the crimp; the results are then expressed as theratio between the measured lengths of the individual filaments and saidpredetermined cut length.

The striations in the web can be produced by passing the spread webunder tension past a plurality of filament deflecting elements spaced'widthwise of the web, e.g. by passing the spread web over a rotatingroll having a series of regularly spaced parallel circumferential ridges'which serve to deflect the longitudinal filaments widthwise of the bandand to thereby increase the con centration of the filaments between theridges. There may be, for example, about 50 to 500, preferably about to400, ridges per foot of width of the web, to produce to a correspondingnumber of parallel striations in the web.

Striations may also be introduced prior to the spreading operation. Forexample, in a preferred type of crimpderegistering operation, the towband is subjected to a differential gripping action during which itpasses in contact with a roll having circumferential grooves (e.g.having a continuous helical groove or a series of independent completelyparallel grooves); the resulting deregistered band often showsstriations which are generally eliminated or greatly reduced as the webis air-spread in a series of stages, particularly when the filamentscarry a finish which permits the filaments to slide over each othereasily. When, however, a more sticky or scoopy finish (such as certainmineral oil formulations) is employed which inhibits migration offilaments from the dense to the lean bands of the striated material, thestriations can persist through the spreading operation. When the groovesand ridges of the crimp-deregistering roll are helical, the resultingstriations run at a small angle (e.g. 2) to the precise lengthwisedirection of the web.

In the preferred forms of the invention, the parallel, dense bands ofthe striated web are not independent of each other, but are heldtogether by individual filaments part of whose length lies within thesedense bands and part of whose length lies in the adjacent lean bands.Some of these tying filaments completely traverse an adjacent lean band,usually at a small angle to the longitudinal direction of the web, sothat a singe filament appears in two or more of these parallel densebands, at points separated along the length of the web. Others of thesetying filaments do not completely traverse an intervening lean band but,instead, overlap other similar filaments extending from a dense band onthe other side of that lean band; the frictional engagement of theseoverlapping filaments helps to tie together the dense bands in theirspacer relationship.

Typically, the filament density in the dense bands is about 1.5 to 10times the filament density in the lean bands. There is usually a gradualvariation in the filament density from the dense to the lean bands, e.g.a plot of filament densities across the width of the striated Web isusually of sinusoidal, rather square-wave, form.

Setting of the striated web is preferably effected by passing the webbetween heated calender rolls while the filaments of the web are in aheat-plasticizable condition or carry a heat-softened material. Forexample, when the filaments are of the usual secondary cellulose acetate(containing, for example, about 2 /2 acetate groups per anhydroglucoseunit) the addition of some water to the filaments (as by spraying theweb with water or by supplying a water-wet tow to the deregistering andspreading operation) so that the web carries, for example, enoughsurface water to feel at least damp to the touch, will cause the web tobe temporarily plasticized when it is subjected to calender rolls havingsurface temperatures of, for example, about 250 F. to about the meltingpoint of the fiber. The resulting calendered web is stiffened by thistreatment; its filaments are bonded together at spaced contact points;preferably, however, it still retains a soft cloth-like limpness andfoldability.

Other setting techniques involve dusting, the striated web with smallamounts of a thermoplastic powder (e.g. polyvinyl chloride) or sprayingthe web with a dispersion (e.g. a latex or solution in volatile solvent)of a thermoplastic material (e.g. an acrylic resin, such as polyethylacrylate or other vinyl resin such as polyvinyl acetate) or spraying itwith a plasticizer (other than the water previously described) such astriacetin or an acetone-water mixture, followed by hot calendering orpassage through a heated oven, to bond the fils at spaced contactpoints.

After the setting step, the striated web is cross-lapped. Variouscross-lapping techniques, including those described below with referenceto the drawings, may be used. The angle of cross-lapping is preferablyabout 90 in which case the final product has the appearance of asquare-woven fabric. The cross-lapping may be effected so as to producea structure whose thickness is made up of two or more (e.g. 2, 3, 4 ormore) layers of the striated web.

The cross-lapped structure is treated to bond its layers together. Thismay be effected, for example, by typical saturation techniques (RandoBonder), spray bonding, etc., commonly used for making non-wovenfabrics, as disclosed for example in the Man-Made Textile Encyclopedia,edited by J. J. Press, published 1956 by Text Book Publishers, Inc., pp.485 to 489. The thickness of the resulting bonded structure is typicallyin the range of about 2 to 10 mils.

Certain aspects of this invention are illustrated in the accompanyingdrawings in which:

FIG. 1 is a schematic view of the deregistering, spreading, striatingand setting operations.

FIG. 2 is a schematic view of one type of cross-lapping operation, inwhich a wound roll of the spread web is used.

FIG. 3 is a view of the flat cross-lapped material produced in theoperation of FIG. 2, partly unfolded to show its structure.

FIG. 4 is a schematic view of the wrapping of sanitary napkins by across-lapping operation, using two rolls of spread webs.

FIG. 5 is a plan view of a calendered striated web.

FIG. 6 is a view of a striating roll used in the process of FIG. 1.

In the process illustrated in FIG. 1, the crimped tow band 11 is drawnfrom a bale 12 through a banding jet 13 in which air is blown at the towso that it emerges as a flattened band of a width of, for example, 8inches. This band passes around adjustable stationary tensioning bars 14which help to smooth and uniformly pretension it, then into the nipbetween a pair of rubber-surfaced rolls 16, 17, driven at a constantspeed, and horizontally to the nip between a rubber-surfaced roll 18 anda driven grooved steel roll 19, which has helical threads (e.g. 14threads per inch, the crests of the threads being flat and about ,6 inchwide). The tow band, whose crimps have been thus deregistered, thenpasses through a pair of air spreaders 21 and 22 in each of which air isblown transversely at the tow band, so that it is spread in two stagesto a width of say 50 inches. Before entering the second spreader 22, andafter leaving that spreader, the tow makes S-wraps about a pair of rolls23, 24 and a second pair of rolls 26, 27. The lower roll of each of thepairs of rolls herein described is positively driven at a constant speedwhile the corresponding upper roll is pressed downwardly, by anysuitable loading device, so that each upper roll is driven by frictionalcontact with the toW or web on the lower roll of the pair. Rolls 17, 24and 26 are driven at about the same linear surface speed while roll 19is driven at a linear surface speed about 1 /2 times that of theserolls. After leaving the rolls 26, 27 the web is passed over a groovedstriating roll 28 having 10 to 100 grooves/in. then between a pair ofdriven heated calender rolls 29, 31 to take up roll 32. The roll ofmaterial is then crosslapped by hand so that the striations of thetopmost layer cross those of the lower layer at a angle. This is thensprayed with acrylic bonding resins, dried in an oven, and subsequentlycalendered to achieve intimate bonding of the layers.

In the process illustrated in FIG. 2, one starts with a roll 41 of setstriated web material, produced by rolling up the web directly after ithas been calendered and cooled. The roll 41 is then mounted so as tounroll the web material in one direction while the axis 42 of the roll41 is rotating in a plane generally perpendicular to the direction inwhich the web material is being taken off. After leaving the roll 41,the web material, which is in a generally helical configuration, passesbetween a pair of rolls 43, 44 which serve to flatten it, producing aflat cross-lapped structure 46 whose striations make angles of about 45to its edges.

For effecting the simultaneous rotation of the roll 41 about its axis 42while the axis is itself being rotated, the roll may be mounted on anaxle which is journalled for free rotation in bearings 47 carried bygear-toothed pinions 48, the teeth of the pinions being meshed with theteeth of a ring gear 49 which is rotated, by a suitable drive mechanism,in the direction shown by the arrow in FIG. 2. The pull of the drivenrolls 43, 44 causes the roll 41 to unwind during the rotation of itsaxis. When the relative speeds of the rolls 43, 44 and the ring 49 aresuch that the axis 42 rotates 360 while the surfaces of roll 43 or 44move a distance equal to twice the width w of the rolled web, the filsof the flat cross-lapped structure 46 will be at an angle of 90 to eachother and the structure will be made up of a single striated web foldedin a series of overlapping parallelograms P (see FIG. 3), one pair ofsides of each parallelogram being along the fold lines 51, whichconstitute the edges of the flattened structure, and the other pair ofsides 52 of each parallelogram (which sides correspond to the edges ofthe original web) being at 45 to said fold lines. The flattenedcross-lapped structure is then bonded and taken up on a rollcontinuously.

In the process illustrated in FIG. 4, a preformed heavy card silver 61of parallel staple fibers (which silver is of a weight and absorptivecharacter suitable for a sanitary napkin core) is passed successivelythrough two driven rotatable parallel rings 62 and 63 on each of which aroll 64, 65 of set striated web material is rotatably supported. Therings 62, 63 are rotated in opposite directions at equal angular speeds,their rates of rotation being such, in relation to the speed at whichthe rope 61 is pulled through said rings, that each layer of webmaterial is wound at a 45 angle to the axis of the silver. The surfaceof the resulting structure is then sprayed lightly with a dispersion ofan acrylic resin and then flattened by passage through hot calenderrolls.

In other aspects of this invention, the cross-lapping techniquesillustrated in FIGS. 2 to 4 may be also employed With spread webmaterials which are not striated but which are of more or less uniformdensity across their Widths.

The filaments used in this invention may be, as previously mentioned, ofpolyethylene terephthalate or secondary cellulose acetate (of the usualacetyl content, e.g. about 54-55% calculated as acetic acid). It iswithin the broad scope of this invention to use other filamentarymaterials such as other polyesters (e.g. the terephthalate esters ofother glycols, such as 1,4-dimethylol cyclohexane), linearsuperpolyamides (such as nylon-6, nylon-6,6, nylon-4, nylon-11, orhexamethylene terephthalamide), melt-blended polyamide-polyestercombinations, acrylics such as polyacrylonitrile and acrylonitrilecopolyrners, modacrylics, olefin polymers and copolymers, e.g. isotacticpolypropylene, other organic derivatives of cellulose, such as esters orethers, such as cellulose triacetate, cellulose propionate celluloseacetate propionate, or the like, rayon (regenerated cellulose), etc. Thenumber of filaments in the starting tow can vary within wide limits,e.g. about 1000 to 1,000,000 preferably about 4000 to 20,000, with adenier per filament of about 1 to 20. The number of crimps per inch inthe filaments may be, for example, as high as about '80, but for mostproducts described herein it will be in the range of about 5 to 20,preferably about 8 to 12, crimps per inch. The linear densities of thespread webs may be, for example, within the range of about /s to 1 ounceper square yard, preferably within the range of about A to /2 ounces persquare yard. The striation frequency, i.e. the number of lean bands perfoot of web width, may be, for example, in the range of about 50 to 500,preferably about 100 to 400.

The foregoing detailed description has been given for clearness ofunderstanding only and no unnecessary limitations are to be understoodtherefrom. The invention is not limited to the exact details shown anddescribed, for obvious modifications will occur to those skilled in theart. The Abstract given above is for the convenience of technicalsearchers and is not to be used for interpreting the scope of theinvention or claims.

What is claimed is:

1. Process for the production of non-woven fabrics which comprisestensioning a band of crimped, substantially parallel continuousfilaments to smooth and uniformly pretension the band,

deregistering the crimps of the filaments of the band to form a web,

spreading the web of filaments,

striating the web of crimped parallel filaments to produce alternatingdense and lean lengthwise bands therein,

setting the striations in the web,

cross-lapping said web to produce a layered structure,

a bonding adjacent layers of the cross-lapped striated web to produce anon-Woven fabric having the appearance of a woven fabric.

2. Process as in claim 1 in which the striation frequency in said web isabout to 500 striations per foot and the density of said web is about /8to 1 ounce per square yard.

3. Process as in claim 1 in which the Web has regularly alternatingparallel dense and lean bands held together by tying filaments part ofwhose length lies within these dense bands and part of whose length liesin the adjacent lean bands, some of said tying filaments completelytraversing a'lean band at a small angle to the longitudinal direction ofthe web so that such filament appears in a plurality of said dense bandsat points separated along the length'of the web, and others of saidtying filaments incompletely traversing a lean band and overlapping, andin frictional engagement with other similar tying filaments extendingfrom the opposite side of said lean band.

4. Process as in claim 3 wherein the step of spreading comprisesair-spreading the deregistered band of said crimped parallel filamentsand the step of tensioning comprises passing the spread Web undertension past a plurality of filament deflecting elements spacedWidthwise of the web.

5. Process asin claim 4 in which said deflecting elements arespacedridges on a rotating roll having its axis transverse to said web.

References Cited UNITED STATES PATENTS 1,108,354 8/1914 Fowler 1562041,885,280 11/1932 Moore 156-177 X 2,315,851 4/1943 Goldman 1562042,503,067 4/ 1950 Powell 156204 X 2,635,322 4/1953 McDermott 156-204 X2,723,705 11/1955 Collins 156177 3,041,230 6/1962 Diehl 156172 3,132,9865/1964 Goldman 156177 X 3,345,230 10 /1967 McClean 156-181 3,365,3461/1968 Fritz et al 156-180 X FOREIGN PATENTS 614,547 5/1934 Germany156227 OTHER REFERENCES Def. Pub. Ser. No. 785,020 on Apr. 1, 1969 toFritz, filed Apr. 18, 1966.

BENJAMIN R. PADGETT, Primary Examiner R. S. GAITHER, Assistant ExaminerU.'S. Cl. XJR.

